lacrimal apparatus
Post on 16-Jul-2015
213 Views
Preview:
TRANSCRIPT
Lacrimal apparatus
It is concerned with the tear formation & transport.
Lacrimal passage includes :
• Lacrimal gland• Conjunctival sac• Lacrimal puncta • Lacrimal canaliculi• Lacrimal sac• Nasolacrimal duct
Osteologyo The lacrimal sac is a depression in
inferomedial orbital rim .
o Maxillary and lacrimal bones.
o Bordered by the anterior lacrimal crest (maxillary bone) & posterior lacrimal crest (lacrimal bone).
• The nasolacrimal canal originates at base of lacrimal fossa.
• Formed by the maxillary bone laterally and the lacrimal and inferior turbinate bones medially.
• The width of superior opening is 4–6 mm.
• The duct courses posteriorly and laterally in the bone for 12 mm to drain into the inferior meatus of the nasal cavity.
Secretory system
• It includes lacrimal gland, accessory glands
• Lacrimal gland is above & anterolateral to
globe.
• Secretes tears into superior fornix.
• Tears moisten & lubricates the : cornea ,
conjunctiva.
Lacrimal gland
• Yellowish soft lobulted serous gland.
• It consists of
Large Orbital Part
Smaller Palpebral Part
The orbital part
• It has the shape and size of an almond.
• Lodged in the lacrimal fossa in the anterolateral part of the roof of the orbit
• Posterior to the orbital septum
The palpebral part
• ⅓ size of the orbital part.
• Lodged in the lateral part of upper eyelid.
• Continuous with the orbital part around the lateral margin of the aponeurosis of the levator palpebrae superioris.
Accessory glands
• Are small, compound, branched, tubular glands .
• Located in the middle of lid (Wolfring glands) or superior & inferior fornices (Krause glands).
• Ectopic portions of lacrimal gland tissue .
Blood supply
• Artery supply : Lacrimal artery , branch of ophthalmic artery.
• Venous drainages : Ophthalmic Vein.
• Lymphatic drainage : Joins that of conjunctiva & drain into the preauricular lymph nodes.
Nerve supply
• Parasympathetic :
The parasympathetic secretomotor fibres are drivedfrom the lacrimal nucleus of facial nerve .
They reach the Sphenopalatine ganglion via the Greater superficial petrosal nerve
The postganglionic fibres join the Maxillary nerve then through its Zygomatic nerve and further
through its Zygomticotemporal branch
They join the lacrimal nerve by a communication between it and zygomaticotemporal nerve.
They reach the gland through lacrimal nerve.
Some postganglionic fibres from the sphenopalatine ganglion reach the gland through the periosteum of the orbit via its orbital branches.
• Sympathetic :
From carotid plexus
• Sensory : lacrimal nerve , branch of
ophthalmic division of trigeminal nerve.
Duct system :
• The gland has about 12 short, slender ducts.
• They arise from the lower surface of the gland.
• Open into the lateral part of the superior fornix of the conjuctiva.
Flow of tears
• The lacrimal secretion flows down and is pushed medially by the movements of the eyelids.
• The tears moisten the eye and accumulate in the Lacus Lacrimalis which is a triangular depression between the medial parts of both eyelids.
• It is drained by the Lacrimal canaliculi to the lacrimal sac.
• From the sac it descends through the Nasolacrimal duct to reach the inferior meatus of the nose.
Lacrimal canaliculi :
• They are two slender ducts 10 mm in length.
• They run in the medial parts of the margins of both eyelids.
• Each duct begins by an opening called Lacrimal Punctum on the summit of an elevtion called Lacrimal Papilla.
• They drain the lacrimal fluid into the Lacrimal Sac.
Lacrimal sac :
• This is a small sac lodged in the lacrimal groove.
• It is about 12 mm in length having blind upper and lower ends.
• The lower end is continuous with the Nasolacrimal duct.
• It is covered by lacrimal fascia, which separates the lacrimal sac from the medial palpebral ligament anteriorly and from the lacrimal part of orbicularis oculi posteriorly.
Nasolacrimal duct :
• This is a tube , half an inch in length runs through the nasolacrimal canal.
• It begins from lower end of the lacrimal sac, run downwards, backwards and laterally to open into the anterior part of the inferior meatus of the nose.
The lower end of the duct is guarded by a mucous fold called lacrimal fold, which acts as a valve preventing nasal secretion from ascending
up into the duct.
top related